Fracture Estimation and Characterization
The development of naturally fractured reservoirs is significantly influenced by the characteristics of the fracture network since these control the volume and flow direction of the fluid through the reservoir rocks.
The knowledge of fracture characteristics provides many benefits:
Fracture analysis using shear wave splitting
- Enables optimized placement of injectors for improved sweep efficiency and better control of the reservoir pressure.
- Enables prediction of preferential flow paths which may lead to premature water breakthroughs or, conversely, act as barriers to impede production.
A good understanding of the fracture network in terms of intensity, orientation, and spatial distribution is therefore essential for improved reservoir development.
Fracture information can be obtained from:
- Core observations and image log interpretation
- provide fracture characterization on a centimeter scale
- these data are only valid in the vicinity of the borehole and when extrapolated beyond this lead to erroneous prediction of the overall reservoir mechanics
- Structural interpretation and basin models
- describe faulting on a kilometer scale
- obtained from conventional seismic data volumes
- Seismic azimuthal anisotropy
- describes fractures in the 10m range
- CGG derives fracture density and orientation from anisotropy measurements obtained from
- shear wave splitting from multicomponent data
- pre-stack measurements of VVAZ (velocity variation with azimuth) and AVAZ (amplitude variation with azimuth) followed by fracture analysis using FractAL
- Inversion for isotropic elastic parameters using simultaneous inversion
- attributes extracted from limited angle and azimuth-sectored stacked cubes using FracVista
In order to obtain accurate azimuthal anisotropy measurements, the seismic data must be sampled at as many azimuths as possible, therefore wide azimuth, or multi-azimuth data, are a pre-requisite for fracture characterization.